#!/usr/bin/env python3
"""Make exported SVGs themeable without flattening their tones.

    python3 tools/svg_currentcolor.py <dir> [--dry-run]

Figma and most icon exporters bake a literal colour into every path
(`fill="#141B34"`). Painting over that in Flutter means
`ColorFilter.mode(c, srcIn)`, which repaints *every* path one colour — fine for
stroke and solid, fatal for twotone/duotone/bulk, where the second tone is the
whole point.

This rewrites the colour to `currentColor` and leaves opacity alone, so
`SvgPicture.asset(..., theme: SvgTheme(currentColor: c))` tints the icon while
its own `fill-opacity` / `stroke-opacity` keep the tones apart.

Multi-*hue* artwork (two genuinely different colours, not two opacities) can't
survive this — those files are reported and skipped.

White is not a second hue. In duotone and bulk a white fill is a knockout: it
covers the tinted layer to cut a shape out of it. Counting it as a colour
skipped half of every duotone set, so the ink around it is recoloured and the
white is left white — right on a light background, and the most flutter_svg
can do, since SvgTheme has no "background colour". (The gallery paints those
shapes with its tile colour instead.)
"""
import re
import sys
from collections import Counter
from pathlib import Path

COLOR = re.compile(r'\b(fill|stroke)\s*=\s*"([^"]*)"')
OPACITY = re.compile(r'(fill|stroke)-opacity\s*=\s*"([0-9.]+)"')

# Figma writes `fill="black"` as readily as `fill="#141B34"`. Matching only hex
# left those untouched, so the icon stayed black and vanished on a dark theme.
NAMED = {
    'black': '#000000', 'white': '#ffffff', 'red': '#ff0000', 'lime': '#00ff00',
    'blue': '#0000ff', 'yellow': '#ffff00', 'cyan': '#00ffff', 'aqua': '#00ffff',
    'magenta': '#ff00ff', 'fuchsia': '#ff00ff', 'silver': '#c0c0c0',
    'gray': '#808080', 'grey': '#808080', 'maroon': '#800000',
    'olive': '#808000', 'green': '#008000', 'purple': '#800080',
    'teal': '#008080', 'navy': '#000080', 'orange': '#ffa500',
}
SKIP = {'none', 'currentcolor', 'transparent', 'inherit', ''}
WHITE = '#ffffff'


def norm(value: str):
    """Canonical #rrggbb, or None when the value isn't a colour to recolour."""
    v = value.strip().lower()
    if v in SKIP or v.startswith(('url(', 'var(')):
        return None
    if v in NAMED:
        return NAMED[v]
    if v.startswith('#'):
        h = v[1:]
        if len(h) in (3, 4):
            h = ''.join(c * 2 for c in h[:3])
        return '#' + h[:6]
    m = re.match(r'rgba?\(([^)]*)\)', v)
    if m:
        parts = [p.strip() for p in m.group(1).replace('/', ',').split(',')][:3]
        try:
            return '#' + ''.join(f'{int(float(x)):02x}' for x in parts)
        except ValueError:
            pass
    return v


def ink(src: str) -> set:
    """The colours to recolour. White only counts when it's all there is."""
    found = {h for h in (norm(m.group(2)) for m in COLOR.finditer(src)) if h}
    return found - {WHITE} or found


def recolor(src: str):
    """`src` with its ink as currentColor, or None when it has two real hues."""
    hues = ink(src)
    # Two distinct hues means real colour, not two opacities of one colour.
    if len(hues) > 1:
        return None
    return COLOR.sub(
        lambda m: f'{m.group(1)}="currentColor"' if norm(m.group(2)) in hues
        else m.group(0), src)


def main() -> int:
    if len(sys.argv) < 2:
        sys.exit(__doc__)
    root = Path(sys.argv[1])
    dry = '--dry-run' in sys.argv
    files = sorted(root.rglob('*.svg'))
    if not files:
        sys.exit(f'no .svg files under {root}')

    changed = skipped = 0
    multihue = []

    for f in files:
        src = f.read_text(encoding='utf-8')
        out = recolor(src)
        if out is None:
            multihue.append((f, sorted(ink(src))))
            skipped += 1
            continue
        if out == src:
            skipped += 1
            continue
        changed += 1
        if not dry:
            f.write_text(out, encoding='utf-8')

    tones = Counter()
    for f in files:
        tones[len(set(OPACITY.findall(f.read_text(encoding='utf-8'))))] += 1

    print(f'{len(files)} svg  |  rewritten {changed}  |  untouched {skipped}'
          + ('   (dry run)' if dry else ''))
    if multihue:
        print(f'\n{len(multihue)} file(s) use more than one hue — left alone, they '
              'need explicit colours rather than currentColor:')
        for f, hues in multihue[:10]:
            print(f'  {f.name:<34} {", ".join(hues)}')
        if len(multihue) > 10:
            print(f'  … and {len(multihue) - 10} more')
    return 0


if __name__ == '__main__':
    raise SystemExit(main())